New York City Mayor Zohran Mamdani marked tax day by making good on one of his most prominent campaign promises, and he did it while outside hedge fund billionaire Ken Griffin’s front door—and the Citadel CEO worth over $51 billion did not like it one bit.
In a video posted on Tax Day by the NYC Mayor’s Office, Mamdani announced the city’s first-ever pied-à-terre tax: an annual fee on luxury properties valued above $5 million whose owners do not live in New York full-time. The video, which has already drawn nearly 470,000 views and 48,000 likes, was shot outside 220 Central Park South, the building where Griffin owns a four-floor penthouse he purchased in 2019 for $238 million, then the highest price ever paid for a home in the United States.
“When I ran for mayor, I said I was going to tax the rich,” Mamdani said in the one-minute clip. “Well, today we’re taxing the rich.”
But a week later, Griffin’s COO at Citadel, Gerald Beeson, hinted the company might not move forward with a massive undertaking in a Midtown construction project.
“We are about to commence the redevelopment of 350 Park Avenue, creating 6,000 highly paid construction jobs and supporting the creation of more than 15,000 permanent jobs in mid-town New York,” wrote Beeson in a letter viewed by the Wall Street Journal. “The project—if we move forward—will entail more than $6 billion dollars of spending.”
Later in the letter, Beeson called out the mayor personally, for personally calling out Griffin. “It is shameful that he used Ken’s name as the example of those who supposedly aren’t carrying their fair share of the burdens associated with New York City’s often costly and wasteful spending,” the email said, according to the Journal. “In doing so, the mayor has once again manifested the ignorance and disdain of the elite political class towards those who have been consistently committed to building one of the greatest cities in the world.”
“We have nearly 2,500 colleagues who have chosen to build their careers here,” Beeson wrote in the letter, the Journal reported. “We understand that our hard work and success will, on occasion, make us targets for political rhetoric. But it should not diminish the pride we take in building firms that will continue to help New York City thrive for decades ahead.”
Mamdani’s campaign promise to “Tax the Rich”
The pied-à-terre tax, which is backed by Gov. Kathy Hochul and still requires approval from the state legislature, would apply to one-to-three-family homes, condominiums, and co-ops worth over $5 million when the owner’s primary residence is outside New York City. Mamdani’s office estimates the tax would generate at least $500 million annually, with revenue directed toward free childcare, street cleaning, and neighborhood safety.
Griffin relocated Citadel’s headquarters from Chicago to Miami in 2022, drawn by Florida’s lack of a personal income tax. He shares the move with Jeff Bezos, Mark Zuckerberg, and Google cofounders Larry Page and Sergey Brin, all of whom recently left high-tax states and now maintain Florida residences. Griffin also recently paid $38 million for a duplex apartment up the block from where Mamdani shot the video, according to the Wall Street Journal.
Mamdani said the tax would fix “a fundamentally unfair system.” “These units are sitting empty,” he said. “And even so, they’re able to reap the huge financial rewards of owning property in, dare I say, the greatest city in the world.”
The pied-à-terre tax has circulated in New York policy circles for years but has repeatedly stalled in Albany. Mamdani recently pushed a wealth tax in New York but said the city would be forced to instead increase property taxes if the tax didn’t get state approval. Neither Griffin nor the mayor’s office responded to Fortune’s request for comment.
In a post on X a few days after the video was published, billionaire Pershing Square CEO Bill Ackman backed Griffin and Citadel in the public back and forth.
“Non-residents who spend millions of dollars on NYC apartments help drive NYC’s economy,” wrote Ackman. “The Ken Griffins of the world make NYC high end development viable, driving high-paying construction, brokerage, legal, marketing, and other jobs in NYC. We should be applauding Ken for spending $238 million in NYC, not attacking him for doing so.”
A version of this story was published on Fortune.com on April 16, 2026.